Students are given the graph of a y= parabola. They are able to move the focus and directrix while studying the changes in the parabola equation (particularly the x^2 coefficient, "a", which determines the parabola shape). They discover that the distance between the focus and directrix, "m", is inversely proportional to "a" - in particular, it can be proved that a = 1/(4m). Students may also study the sign of "a" as they move the focus above and below the directrix.
